ts 之 属性的修饰符public、private、protect

public修饰的属性可以在任意位置访问和修改

class Animal{
    
    name: string //等同于 public name: string; public是默认修饰符 
    age: number

    constructor(name: string, age: number) {
    
        this.name = name
        this.age = age
    }
}

也可以换成如下写法：

class Animal{
    
    constructor(public name: string, public age: number) {
    
    }
}

const a = new Animal('tt', 19)
console.log(a);//Animal {name: 'tt', age: 19}

private修饰的属性是私有属性，私有属性只能在类的内部访问和修改，它的子类也无法访问和修改;它的实例也无法访问

class Animal{
    
    private name: string 
    private age: number

    constructor(name: string, age: number) {
    
        this.name = name
        this.age = age
    }
}

如果想访问private修饰的属性，可以通过 set/get

class Animal{
    
    private _name: string 
    private _age: number

    constructor(name: string, age: number) {
    
        this._name = name
        this._age = age
    }

	get age() {
    
		return this._age
	}

	set age(value) {
    
        if(value>=0) {
    
            this._age = value
        }
	}
}

const a = new Animal('aa', 15)
console.log(a.age);//15
a.age = -33
console.log(a.age);//15
a.age = 19
console.log(a.age);//19

protect受保护的属性，只能在当前类，和它的子类中访问和修改，但是他们的实例都不能访问

class Animal{
    
    protected _name: string 
    protected _age: number

    constructor(name: string, age: number) {
    
        this._name = name
        this._age = age
    }
}

class Dog extends Animal{
    
    test() {
    
        console.log(this._age);
    }
}

const dog = new Dog('小黑', 18)
dog.test()//18